Hepatitis B virus (HBV) infection is a major health problem throughout the world. HBV is a causative agent of both an acute and chronic form of hepatitis. It is estimated that more than 200 million people worldwide are chronic carriers of HBV.
HBV belongs to the family Hepadnaviridae, which includes a number of related viruses that primarily infect small rodents. All members of the hepadnavirus family have a number of characteristics in common such as morphological appearance, antigenic makeup and DNA size and structure. Pathological findings following infection with the members of this family are quite similar. Studies show that the replication and spread of the viruses of this family are dependent upon the reverse transcriptase of an RNA intermediate.
HBV is a double-stranded DNA virus. Its DNA polymerase catalyzes both DNA-dependent and RNA-dependent RNA synthesis. The life cycle of HBV involves the enzyme reverse transcriptase in its DNA replication.
Although acute HBV infections are generally self-limiting, in many instances the disease can progress to the chronic state. HBV infection also creates a risk to fulminant hepatitis. In addition, Hepatitis B viral infections are closely associated with hepatocellular carcinoma.
AIDS is a generally fatal disease caused by a human pathogenic retrovirus known as human immunodeficiency virus (HIV), which includes HIV-1 and HIV-2. Reverse transcriptase plays an essential role in the elaboration and life cycle of HIV and consequently, the progress of the disease. Reverse transcriptase inhibitors are currently used with other classes of anti-viral agents to slow and in some cases halt the progress of HIV infection.
Reverse transcriptase inhibitors are preferred therapeutics for treating certain viral infections, particularly HBV and HIV infections. Typically about 300 mg of a reverse transciptase inhibitor must be administered daily for effective treatment of a viral infections, sometimes on a once per day dosing schedule, but more typically on a twice or three times per day dosing schedule. Because patients suffering from HBV or HIV often take a number of medications, a reverse transcriptase inhibitor efficacious at lower dosages is urgently needed. A reverse transcriptase inhibitor that can be administered once daily or less frequently is particularly desireable.
Elvucitabine is a nucleoside analog of the formula

The anti-viral properties of Elvucitabine have been described previously in U.S. Pat. Nos. 5,621,120, 5,627,160, and 5,839,881, and U.S. patent application Ser. No. 10/411,929, filed Apr. 11, 2004, which are hereby incorporated by reference for their teachings regarding the use of Elvucitabine for treating viral infections, including HBV and HIV infections, and for teachings regarding the chemical synthesis of Elvucitabine.